Investigation of a radiative cooling system with natural circulation for regulating a heat sink

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The global energy demand has seen a significant increase over the past decade. Our inseparable need for energy has created a number of serious concerns. The most important concern is the environmental impact of our energy generating methods. Another looming concern is our global fossil fuel resources that are diminishing progressively. These two major concerns have turned attention to research and development of energy efficient and alternative energy systems.
A field of alternative energy that has been untapped is nocturnal radiative cooling. The idea behind this is to utilise the cooling effect between a hot surface and the night sky. The setup is similar to that of a solar water heating system but is used for cooling instead of heating.
Previous studies on radiative cooling systems have all focussed on forced circulation systems. The aim of this study is to analyse the performance of a natural circulating system. The current knowledge on radiative cooling systems is limited and experimental research is often a costly and time consuming exercise. As a result it is difficult to get an understanding of the performance of a radiative cooling system in various operating environments. The aim of this study is to overcome this limitation by developing a theoretical model to simulate the performance of a natural circulating radiative cooling system.
A natural circulating solar water heater model was used as a basis for the natural circulating radiative cooling model. A night sky radiation model replaced the solar radiation component to give the radiative heat transfer of the panel to the night sky. Fundamental heat transfer and fluid flow theories also formed part of the model.
The theoretical model was able to give realistically accurate predictions compared to data from an experimental setup. The model made it possible to study the impact of various parameters on the system performance without the constraints of experimental setups. The performance of a natural circulating radiative cooling system was simulated over a year under different operating climates by using historical weather data.
The results obtained with the help of the model indicated that natural circulating radiative cooling is indeed able to provide a sufficient cooling effect that can be utilised in a practical manner. This study gives indication that radiative cooling systems are worthy of further development to ensure that it forms part of the current line–up of alternative energy systems.